1. Technical Field
The present disclosure relates to an apparatus and related method for electrosurgically sealing tissue. In particular, the disclosure relates to sealing tissue with a series of discrete electrode segments spaced over a targeted region of the tissue.
2. Background of Related Art
Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaws that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaws may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaws. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis, which may facilitate the transection of the sealed tissue. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al.
A bipolar electrosurgical forceps typically includes opposed electrodes disposed on clamping surfaces of the jaws. The electrodes are charged to opposite electrical potentials such that an electrosurgical current may be selectively transferred through tissue grasped between the electrodes. To effect a proper seal, particularly in relatively large vessels, two predominant mechanical parameters should be accurately controlled; the pressure applied to the vessel, and the gap distance established between the electrodes.
Both the pressure and gap distance influence the effectiveness of the resultant tissue seal. If an adequate gap distance is not maintained, there is a possibility that the opposed electrodes will contact one another, which may cause a short circuit and prevent energy from being transferred through the tissue. Also, if too low a force is applied the tissue may have a tendency to move before an adequate seal can be generated. The thickness of a typical effective tissue seal is optimally between about 0.001 and about 0.006 inches. Below this range, the seal may shred or tear and above this range the vessel walls may not be effectively joined.
Certain surgical procedures may be performed more quickly and accurately with an electrosurgical forceps having relatively longer electrodes than one having shorter electrodes. To this end, electrosurgical forceps have become available with electrodes 60 mm in length or more. Longer electrodes, however, may tend to present difficulties in maintaining a uniform pressure and gap distance, and thus, creating an effective seal along the entire length of the jaws may prove difficult. For example, where a pair of jaws is pivotally coupled by a pivot pin at a proximal region of the jaws, the effects of manufacturing tolerances may be amplified according to a longitudinal distance from the pivot pin. Tissue captured at a distal region of the jaws may thus encounter greater gap distances and lower clamping forces than tissue captured at a proximal region near the pivot pin. This non-uniformity may make it difficult to adequately control the necessary mechanical parameters to generate an effective seal along the entire length of the electrodes.
Also, longer electrodes may tend to have greater power requirements than shorter electrodes. Current up to 5 amps may be drawn by longer electrodes, which is near a limit set for some commercially available electrosurgical generators.